FortifySteve

Hi Guys,

Workin on a swap into my 84 K20. I got a gen iv 5.3 with the VVT/AFM stuff still in it. I want to keep that stuff, itll be trekkin 100 miles a day for my commute.
Ive got a nv4500 and a non vss np241c transfercase. Here lies the issue, I only have a mechanical speedo output. I have researched my *** off trying to find a definitive answer.. the only thing that I have come up with is a couple of loose ends.
Idea 1, run the mech speedo through a dakota digital vss converter then into the TCM via the SGI-5E

Idea 2, Run the mech speedo through the SEN-01-4160 and straight into the E38 on the 71-72 pin VSS high input.

Idea 3 ditch the mech speedo, and use this SEN01128 pulse generator that supposedly will generate the proper pulse output..

Idea 4 sell the manual and swap a 4l80 into the truck instead.. Not ideal but it would work.

anybody do this with a t56 or similar and use an external vss?? I know its not super common..
thanks.

Goldhawg

iTrader: (7)

I used a Speedhut GPS speedo for mine. Don't recall the speedo being a real problem (probably because I was just going GPS), my issue was the tach--never could get a signal off the ECU to drive the tach and had to splice into an injector line per speedhut.

-TheBandit-

iTrader: (1)

I tried this on my originally-auto E38 and it will not respond to VSS input on those pins. I think the OS expects the VSS signal to come from the transmission over serial (GMLAN). My tuner fiddled with it quite a bit and we couldn't get it to do anything other than report a solid 158mph at all times. I have been driving around without any problems.

I read somewhere you can get put a TCM in place and it will take the VSS signal and broadcast it over LAN, but I haven't tried that myself personally.

FortifySteve

So i have discovered that my current transfercase could be retrofit with the vss from the next year very easily. So i am going to order those parts, from what I was told It will be the factory GM 40Pulse per rev. Well see how that turns out!

Goldhawg

iTrader: (7)

I likewise cruise continuously at 158! Just some minor bucking before going closed loop in parking lots w/o stepping on the gas. Once I get her going no issues...

Jimbo1367

CAM on here has a L92 w/ Pat G custom VVT cam and a manual. Try a SEARCH.

FortifySteve

Been running no VSS since day 1 and actually have no issues.. I set the Idle to 800 rpm and disabled the DFCO and COT, I actually got the speedo converter from Dakota the other day only to find out my ECU plug was not pinned for the negative side of the REPTOS connection, so I have to order the crap from Molex to even test that.
Ive been driving this all last week and have had really no issues that I can tell are from no VSS..

LY6CJ7

Resurrecting this thread because I have exactly the same issue - LY6/E38/manual transmission/No VSS - mine wont rev past 4000rpm, but otherwise drives fine (though it does rev hang a bit between shifts). I've had a local tuner working on it with limited success (it will work for a little while, then revert back to nothing over 4000 rpm). I have a Dakota Digital Sen -01-128 (GM 128000 ppm) that I was going to try as a VSS source from the mechanically driven speedo output from my Tcase. But I have no idea how to wire it directly into the ECM (I have no TCM). Some posters have commented that the X1 Pin 71 is the high VSS input, but I not sure how to access that (as in I haven't messed with the ECM plug wiring before). Any thoughts?

-TheBandit-

iTrader: (1)

I have an LY6/E38 with a TH400 behind it. Installed a Dakota Digital VSS into the transmission and wired it into the ECM but the ECM doesn't seem to do anything with the signal. From what I understand if the E38 has an auto OS on it, it expects to get the VSS from the TCM over serial and it will ignore the inputs directly on the ECM connector. It defaults to 158mph.

In other words, I don't think wiring the VSS to the ECM is going to do anything for you anyway. I can explain how to add pins to your connector if you, but I don't expect it will help you.

The 4000rpm issue is probably not related to the VSS at all. I don't have that issue on mine. You may have some other problem like a fuel shortage.

FortifySteve

FortifySteve

LY6CJ7

Thanks for the replys to my thread necropsy.

Interestingly if I have my tuner reflash the tune (including all the various torque management/TPS/rpm limits/manual-auto settings), it will work and rev happily to redline without any issues. It pulls strong to the redline without complaints and I've had the tuner ride along and look at parameters on the fly with no issues. But several hours/and or key cycles and it will revert back to a hard stop at 4000 rpm. It is just like hitting the rev limiter normally and cycles between full and 0 throttle every second or so.

Similar issues by a variety of folks in this thread:
https://forum.hptuners.com/showthrea...-past-4000-RPM

Some have fixed it with a tune, and some have not found a permanent fix.

My tuner is a little inconvenient to get to (about 45 min away), and hasn't been speedy and getting me the tune to post up and send to folks who have inquired they would take a look (thanks to those folks )
Should I(can I) just buy an HP Tuners MPVI2 myself to access this information for now and in the future? Would I need to purchase a "credit" to be able to see the tune that my tuner has already done or can I buy one without a credit?

-TheBandit-

iTrader: (1)

Does yours "rev hang" at all? With my LY6/TH400 combo, if I rev the engine in park or neutral, after I let off, the rpm floats down pretty slowly. I wish it would just snap back down but it doesn't really cause any problems with the auto. I am wondering how it's going to feel when I put in a manual.

LY6CJ7

Mine does rev hang for several seconds.

FortifySteve

That sounds really strange to me, I suspect possibly something else is at play here, some kind of dtc or something isn’t right.. I’ve been driving mine for 30k miles and haven’t had anything like that happen.
As far as the rev hang it’s non existent, I cured that by reducing the timing in the base idle table so it came back down properly. Some of it was minimum air but most of it was cured with reducing timing only on the areas I saw it tracking in the scanner as it came down from a rev.

FortifySteve

LY6CJ7

I've bought an HPTuners MPVI 2 and pulled the tune. It looks like there were some more trans torque management setting that needed to be adjusted. I'll be fixing that up shortly and report back. Referenced in this thread:

https://forum.hptuners.com/showthrea...ny-with-no-TCM

That being said - I have everything to VVT delete and a BTR Stage 2 Truck Cam coming for the motor (as well as a valve train upgrade and refresh).

Project GatTagO

iTrader: (7)

This feature actually helps drivability with a manual transmission a lot. I actually programmed it into my Dominator ECU in the Cougar. I created a table that alters the target idle RPM based on MPH.

Andrew

Andrew Miller

​​​​​​​Any update yet? I have the 4K rev limiter issue as well.

-TheBandit-

iTrader: (1)

That makes sense. Sort of a rev-matching feature.